Synthesis, Crystal Structures, and Ion Pairing of κ6N^6N Complexes with Rare‐Earth Elements in the Solid State and in Solution

The rare earth element complexes (Ln=Y, La, Sm, Lu, Ce) of several podant κ$^6N$-coordinating ligands have been synthetized and thoroughly characterized. The structural properties of the complexes have been investigated by X-ray diffraction in the solid state and by advanced NMR methods in solution. To estimate the donor capabilities of the presented ligands, an experimental comparison study has been conducted by cyclic voltammetry as well as absorption experiments using the cerium complexes and by analyzing $^{89}$Y NMR chemical shifts of the different yttrium complexes. In order to obtain a complete and detailed picture, all experiments were corroborated by state-of-the-art quantum chemical calculations. Finally, coordination competition studies have been carried out by means of $^1$H and $^{31}$P NMR spectroscopy to investigate the correlation with donor properties and selectivity

Luminescent conjugates between dinuclear rhenium complexes and 17α-ethynylestradiol: synthesis, photophysical characterization, and cell imaging

Three new luminescent conjugates between dinuclear rhenium complexes and an estradiol, namely E2-Re, are described. The derivatives have the general formula [Re2(\u3bc-Cl)2(CO)6(\u3bc-R-pydz-17\u3b1-ethynylestradiol)] (R-pydz = functionalized 1,2-pyridazine), where the estradiol moiety is covalently bound to the \u3b2 position of the pyridazine ligand. Different synthetic pathways are investigated, including the inverse-type [4 + 2] Diels Alder cycloaddition reaction between the electron poor 1,2,4,5-tetrazine and 17\u3b1-ethynylestradiol for the synthesis of E2-Re1. The three E2-Re conjugates are purified on silica gel and isolated in a spectroscopically pure form in moderate to good yields (28-50%). All the E2-Re conjugates are comprehensively characterized from the spectroscopic and photophysical points of view. Cellular internalization experiments on human MCF-7 and 231 cells are also reported, displaying interesting staining differences depending on the nature of the spacer linking the estradiol unit to the organometallic fragment. Furthermore, the suitability of these conjugates to also stain simple multicellular organisms, i.e. Ciona intestinalis embryos and larvae at different stages of development, is reported here for the first time

A comparative antimicrobial and toxicological study of gold(III) and silver(I) complexes with aromatic nitrogen-containing heterocycles: synergistic activity and improved selectivity index of Au(III)/Ag(I) complexes mixture

Five aromatic nitrogen-containing heterocycles, pyridazine (pydz, 1), pyrimidine (pm, 2), pyrazine (pz, 3), quinoxaline (qx, 4) and phenazine (phz, 5) have been used for the synthesis of gold(III) and silver(I) complexes. In contrast to the mononuclear Au1-5 complexes all having square-planar geometry, the corresponding Ag1-5 complexes have been found to be polynuclear and of different geometries. Complexes Au1-5 and Ag1-5, along with K[AuCl4], AgNO3 and N-heterocyclic ligands used for their synthesis, were evaluated by in vitro antimicrobial studies against a panel of microbial strains that lead to many skin and soft tissue, respiratory, wound and nosocomial infections. All tested complexes exhibited excellent to good antibacterial activity with minimal inhibitory (MIC) values in the range of 2.5 to 100 mu g mL(-1) against the investigated strains. The complexes were particularly efficient against pathogenic Pseudomonas aeruginosa (MIC = 2.5-30 mu g mL(-1)) and had a marked ability to disrupt clinically relevant biofilms of strains with high inherent resistance to antibiotics. Moreover, the Au1-4 and Ag1-5 complexes exhibited pronounced ability to competitively intercalate double stranded genomic DNA of P. aeruginosa, which was demonstrated by gel electrophoresis techniques and supported by molecular docking into the DNA major groove. Antiproliferative effect on the normal human lung fibroblast cell line MRC5 has also been evaluated in order to determine therapeutic potential of Au1-5 and Ag1-5 complexes. Since the investigated gold(III) complexes showed much lower negative effects on the viability of the MRC5 cell line than their silver(I) analogues and slightly lower antimicrobial activity against the investigated strains, the combination approach to improve their pharmacological profiles was applied. Synergistic antimicrobial effect and the selectivity index of 10 were achieved for the selected gold(III)/silver(I) complexes mixtures, as well as higher P. aeruginosa PAO1 biofilm disruption activity, and improved toxicity profile towards zebrafish embryos, in comparison to the single complexes. To the best of our knowledge, this is the first report on synergistic activity of gold(III)/silver(I) complexes mixtures and it could have an impact on development of new combination therapy methods for the treatment of multi-resistant bacterial infections.Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3334

Magnetic systems at criticality: different signatures of scaling

Different aspects of critical behaviour of magnetic materials are presented and discussed. The scaling ideas are shown to arise in the context of purely magnetic properties as well as in that of thermal properties as demonstrated by magnetocaloric effect or combined scaling of excess entropy and order parameter. Two non-standard approaches to scaling phenomena are described. The presented concepts are exemplified by experimental data gathered on four representatives of molecular magnets.Comment: 33 pages, 16 figure

A comparative antimicrobial and toxicological study of gold(III) and silver(I) complexes with aromatic nitrogen-containing heterocycles: synergistic activity and improved selectivity index of Au(III)/Ag(I) complexes mixture

Five aromatic nitrogen-containing heterocycles, pyridazine (pydz, 1), pyrimidine (pm, 2), pyrazine (pz, 3), quinoxaline (qx, 4) and phenazine (phz, 5) have been used for the synthesis of gold(III) and silver(I) complexes. In contrast to the mononuclear Au1-5 complexes all having square-planar geometry, the corresponding Ag1-5 complexes have been found to be polynuclear and of different geometries. Complexes Au1-5 and Ag1-5, along with K[AuCl4], AgNO3 and N-heterocyclic ligands used for their synthesis, were evaluated by in vitro antimicrobial studies against a panel of microbial strains that lead to many skin and soft tissue, respiratory, wound and nosocomial infections. All tested complexes exhibited excellent to good antibacterial activity with minimal inhibitory (MIC) values in the range of 2.5 to 100 mu g mL(-1) against the investigated strains. The complexes were particularly efficient against pathogenic Pseudomonas aeruginosa (MIC = 2.5-30 mu g mL(-1)) and had a marked ability to disrupt clinically relevant biofilms of strains with high inherent resistance to antibiotics. Moreover, the Au1-4 and Ag1-5 complexes exhibited pronounced ability to competitively intercalate double stranded genomic DNA of P. aeruginosa, which was demonstrated by gel electrophoresis techniques and supported by molecular docking into the DNA major groove. Antiproliferative effect on the normal human lung fibroblast cell line MRC5 has also been evaluated in order to determine therapeutic potential of Au1-5 and Ag1-5 complexes. Since the investigated gold(III) complexes showed much lower negative effects on the viability of the MRC5 cell line than their silver(I) analogues and slightly lower antimicrobial activity against the investigated strains, the combination approach to improve their pharmacological profiles was applied. Synergistic antimicrobial effect and the selectivity index of 10 were achieved for the selected gold(III)/silver(I) complexes mixtures, as well as higher P. aeruginosa PAO1 biofilm disruption activity, and improved toxicity profile towards zebrafish embryos, in comparison to the single complexes. To the best of our knowledge, this is the first report on synergistic activity of gold(III)/silver(I) complexes mixtures and it could have an impact on development of new combination therapy methods for the treatment of multi-resistant bacterial infections

NEW POLYNUCLEAR LUMINESCENT TRICARBONYL RE(I) COMPLEXES CONTAINING MULTI-NITROGEN HETEROCYCLIC LIGANDS

Three different classes of rhenium(I) compounds have been studied in this thesis. New luminescent complexes of general formula [Re2(\u3bc-X)2(CO)6(\u3bc-pydz)] have been synthesized, in which the bridging ancillary ligands are OR- or SR- anions. Intriguing electro-chemical properties have been evidenced, differentiating the OR derivatives from the SR one and the previously reported halide analogues. The bis(benzenethiolato) derivative exhibits a very small electrochemical energy gap and absence of photoluminescence. The best emitting properties, closely comparable to those of the dichloro complex, are shown by the bis(pentafluorophenolato) derivative (\u3a6 = 5.5% in deaerated toluene). A second class involves new neutral dinuclear complexes of rhenium containing bridging 1,2,4-triazole ligands (4-(p-tolyl)-4H-1,2,4-triazole, 4-(n-propyl)-4H-1,2,4-triazole, 4-(4\u2019-nitrophenyl)-4H-1,2,4-triazole). The complexes were designed to obtain a blue shift of the emission compared to the corresponding diazine complexes. The absorption spectra and the electrochemical data show that the rising of the HOMO-LUMO gap has actually occurred, but the intensity of the emission is too weak to have any applicative interest. Experiments trying to obtain complexes in which triazolate ligands coexist with a diazine chromophore are also described. The possible synthesis of analogous derivatives containing 5-aryl tetrazoles (is also under investigation. In both the triazole and tetrazole cases, the new species are examples of a very limited family of molecular complexes in which such ligands are bound to metals in low oxidation state. Finally, the reactions of the unsaturated tetranuclear cluster [Re4(\u3bc3-H)4(CO)12] with diazines bearing substituents in 4 and 5 positions (4,5-bis(trimethylsilyl)pyridazine, 6,7-dihydro-5H-cyclopentapyridazine) and with 1,8-naphthyridine have been performed. The reaction pathways and the influence of the substituents on the fragmentation reactions have been investigated. The photophysical properties of the main reaction products have been preliminary determined

OPTOELECTRONICALLY ACTIVE DINUCLEAR RHENIUM(I) AND MANGANESE(I) COMPLEXES: FROM DESIGN TO APPLICATIONS

Energy is definitely the most important resource for mankind, and sunlight is without any doubt the ultimate energy source.[1] Unfortunately, solar energy is not useful for mankind unless converted into the final usable forms: heat, electricity, and fuels. Conversion of solar energy into heat is straightforward, but conversion of solar energy into electricity or fuel poses several problems, strongly limiting the conversion efficiency.[2] Since we cannot modify the solar spectrum, we need to find materials capable of exploiting sunlight through the threshold mechanism with the highest possible efficiency. Taking into account the average spectral distribution of solar energy, the most favorable threshold is about 885 nm (1.4 eV), which, in principle, allows 33% of energy conversion efficiency.[3] Summing up, the amount of energy we can actually get from the average solar power striking the surface of the earth depends on our capacity of developing the conversion and storage devices we need with the materials we have on our planet. In the last five years, the photovoltaic systems worldwide have undergone substantial development in terms of manufacturing distribution (largely shifted from Europe to Asia), global deployment, and even new photoactive materials.[4] Over 90% of today commercial solar cells are still based on the very same material and basic concepts developed in the 50\u2019s at the Bell Laboratories: light-induced charge separation at a p\u2013n junction between two wafers of p- and n-doped silicon in either single-crystal or polycrystalline form (sc-Si and poly-Si, respectively). The global share of Si PV has increased from 80% in 2009 to over 90% in 2014, because the main competitors, the so called \u201c2nd generation solar cells\u201d, thin film technologies like cadmium telluride (CdTe), copper-gallium-indium selenide (CIGS), and amorphous silicon (a-Si) have grown at a much lower rate.[4] Indeed, Silicon is the second most abundant and uniformly distributed element on the earth\u2019s crust and there is no risk of shortage in any foreseeable future. By contrast, In, Ga, Se, Te, and Cd exhibit a way smaller crustal abundance and, accordingly, they are collected only as byproducts of minerals containing mostly other elements (Cu, Zn, and Al).[5] The third wave of PV technologies entering the market should be based on DSSC and OPV. Expectations for their market debut have been high for years,[6-8] but so far they have materialized only to a very small extent. At present, the market share of these two technologies is still virtually zero, despite a few flagship demonstration projects, which support technical feasibility.[9-10] Compared to the already established technologies, DSSC and OPV can offer easier building integration, in windows and facades, good performances also in non-standard illumination and temperature conditions, and lower requirements in terms of quantity and quality of raw materials. They can be manufactured at smaller economic and energetic cost and their energy payback times are estimated to be shorter than conventional thin-film technologies. The photoactive materials, including dyes, polymeric and small molecular semiconductors, play a key role in influencing physical processes involved in energy conversion, which in turn determine the electrical characteristics of the solar cell. Several types of organic and inorganic dyes are now available, as well as solid-state devices including the redox mediator, as a result of a massive research effort throughout 25 years. Despite the marked increase in the understanding of the DSSC and OPV solar cells, there remain numerous challenges related to cell/module performance and stability that need to be addressed before this technology can be deployed on a large scale. In this Ph.D. thesis we have focused our attention on dinuclear Re and Mn complexes able to act as active materials in optoelectronic applications, such as dye-sensitized solar cells, organic photovoltaics devices (Re) and electrocatalytic reduction of CO2 or H2 generation (Mn). Indeed, considering the state-of-the-art of the knowledge about the dinuclear rhenium complexes containing 1,2-diazine ligands developed in our research group, starting from the pioneering studies on the halide derivatives and their application as dopants in OLED devices and as dyes for bio-imaging, we tried here to extend and tune the properties of these complexes, potentially widening their possible application in various sub-fields of optoelectronics. Therefore, starting from complexes with general formula [M2(\u3bc-X)(\u3bc-Y)(CO)6(\u3bc-R-diazine)] (M=Re, Mn), being X and Y two anionic bridging ligands, we have carried out tailored syntheses with joint experimental and theoretical studies, in order to gain a deeper insight into the electronic processes involved in these classes of compounds. The spectroscopic and/or catalytic properties of the new complexes have been modulated by varying the substituents on the diazine ligand, as well as the nature of the ancillary ligands, thus modulating the LUMO and the HOMO energy level, respectively. Some of these materials were also successfully tested as dyes in DSSC devices. This thesis is basically divided in four main sections 1) New class of Re complexes with lower energy-gap and/or long lived excited state as triplet photosensitizer for triplet-triplet annihilation (TTA) based upconversion 2) New class of hydrido Re complexes and their applications in DSSC solar cells 3) New low-band gap metallo-copolymers based on Re complexes as donors in bulk-heterojunction solar cell 4) New polynuclear Mn complexes containing diazine ligands It is clear that this thesis is the result of a highly multidisciplinary, and therefore collaborative, research work. We have collaborated with various research groups both in Italy and Europe: The electrochemical characterizations have been carried out in collaboration with Prof. Patrizia Mussini (Dipartimento di Chimica, Universit\ue0 degli Studi di Milano, Italy). The theoretical calculation and the molecules\u2019 design, together with the solid state analysis of the complexes, have been performed by Dr. Pierluigi Mercandelli of the same department. The test concerning the TTA upconversion (chapter 4) has been performed in collaboration with Prof. Paola Ceroni (Dipartimento di Chimica, Alma Mater Studiorum - Universit\ue0 di Bologna, Italy). A preliminary photophysical characterization was previously carried out by Dr. Matteo Mauro and Prof. Luisa De Cola (Institut de Science et d'Ing\ue9nierie Supramol\ue9culaires (ISIS), Strasbourg, France). Two different research groups have been involved in the fabrication of the DSSC devices (chapter 5): preliminary tests were performed by Dr. Francesca De Rossi and Prof. Thomas M. Brown (Center for Hybrid and Organic Solar Energy \u2013 CHOSE, Rome, Italy), while the optimization of the cells and a second series of tests has been carried out in collaboration with Dr. Kazuteru Nonomura and Prof. Anders Hagfeldt (Laboratory of Photomolecular Science (LSPM), \uc9cole Polytechnique F\ue9d\ue9rale de Lausanne (EPFL), Switzerland). Dr. Stefania Zappia and Dr. Silvia Destri have been involved in the synthesis and the characterization of the metallo-copolymers (chapter 6) (Istituto per lo Studio delle Macromolecole, Consiglio Nazionale delle Ricerche (ISMAC-CNR), Milan, Italy). [1]N. Armaroli, V. Balzani, Chem. Eur. J. 2016, 22, 32\u201357 [2] N. Armaroli, V. Balzani, Energy for a Sustainable World\u2014From the Oil Age to a Sun Powered Future, Wiley-VCH, Weinheim (Germany), 2011 [3] G. Porter, Criteria for Solar Energy Conversion, in Light, Chemical Change and Life. A Source Book in Photochemistry (Eds.: J. D. Coyle, R. R. Hill, D. R. Roberts), Open University Press, Milton Keynes (UK), 1982, 338 [4] International Energy Agency, Technology Roadmap\u2014Solar Photovoltaic Energy, 2014 https://www.iea.org [5] L. T. Peir\uf3, G. Villalba Mendez, R. U. Ayres, Environ. Sci. Technol. 2013, 47, 2939\u2028 [6] M. Jacoby, Chem. Eng. News 2010, 88 (34), 12 [7] NanoMarkets Report, Dye-Sensitized Cell Markets 2012\u2014Nano-531, 2012, http://ntechresearch.com/market reports/dye sensitized cell markets 2012 [8] International Energy Agency, Technology Roadmap-Solar Photovoltaic Energy 2010, https://www.iea.org [9] \uc9cole Polytechnique F\ue9d\ue9rale de Lausanne, EPFL\u2019s Campus Has the World\u2019s First Solar Window, can be found under https://actu.epfl.ch [10] F. C. Krebs, N. Espinosa, M. Hosel, R. R. Sondergaard, M. Jorgensen, Adv. Mater. 2014, 26, 2

Electrochemical Characterization and CO2 Reduction Reaction of a Family of Pyridazine-Bridged Dinuclear Mn(I) Carbonyl Complexes

Three recently synthesized neutral dinuclear carbonyl manganese complexes with the pyridazine bridging ligand, of general formula [Mn2(μ-ER)2(CO)6(μ-pydz)] (pydz = pyridazine; E = O or S; R = methyl or phenyl), have been investigated by cyclic voltammetry in dimethylformamide and acetonitrile both under an inert argon atmosphere and in the presence of carbon dioxide. This family of Mn(I) compounds behaves interestingly at negative potentials in the presence of CO2. Based on this behavior, which is herein discussed, a rather efficient catalytic mechanism for the CO2 reduction reaction toward the generation of CO has been hypothesized

Dinuclear rhenium pyridazine complexes containing bridging chalcogenide anions : synthesis, characterization and computational study

The synthesis of a series of neutral dinuclear rhenium complexes of the general formula [Re2(m-ER)2(CO)6- (m-pydz)] (pydz = pyridazine; E = S, Se or Te; R = methyl or phenyl; the TeMe is not included) has been carried out via new, either one-pot or two-step, procedures. The one-pot synthesis consists of the oxidative addition of RE\u2013ER across the Re\u2013Re bond of [Re2(CO)10], in the presence of 1 equivalent of pyridazine, and affords the corresponding dinuclear complexes in high yields (ca. 85%). Furthermore, a general two-step procedure has been carried out, which involves the synthesis of heterocubane-like [Re4(m3-ER)4(CO)12] molecules and their reaction with pyridazine, quantitatively affording the corresponding dinuclear species through a symmetric [2+2] fragmentation pathway. The molecular structure of the complexes has been elucidated by single crystal XRD analysis, and TD-DFT calculations predicted the existence of conformers differing in the orientation of the chalcogen substituents with respect to the pyridazine ligand. The relative stabilities and the activation barriers for the interconversion have been calculated, observing a regular trend that has been rationalized depending on the hybridization of the chalcogen atom. Variable temperature NMR studies experimentally confirmed the theoretical prediction, showing, in solution, two conformers with different relative amounts and different interconversion rates between them, depending on the chalcogen nature. From the electrochemical point of view the S, Se and Te complexes display a bi-electronic reversible oxidation peak, differently from the two mono-electronic irreversible oxidation peaks previously observed for the O derivatives. Moreover, a progressive narrowing of the HOMO\u2013LUMO gap on going from O to Te, arising from the increase of the HOMO level, has been observed. This is in line with the decreasing electron-withdrawing strength of the chalcogenide bridging ligand, so that the energy gap for the telluride derivative is 1.64 eV, the smallest value in the whole family of the di-rhenium pyridazine complexes. The spectroscopic HOMO\u2013LUMO gap parallels this trend, with a significant red-shift of the metal-to-ligand charge transfer absorption, making the telluride complex highly promising as a photosensitizer in the field of solar energy conversion. In agreement with the narrow HOMO\u2013LUMO gap, no photoluminescence has been observed upon optical excitation

Supplementary data for article: Senerovic, L.; Zivkovic, M. D.; Veselinovic, A.; Pavic, A.; Djuran, M. I.; Rajkovic, S.; Nikodinovic-Runic, J. Synthesis and Evaluation of Series of Diazine-Bridged Dinuclear Platinum(II) Complexes through in Vitro Toxicity and Molecular Modeling: Correlation between Structure and Activity of Pt(II) Complexes. Journal of Medicinal Chemistry 2015, 58 (3), 1442–1451. https://doi.org/10.1021/jm5017686

Supporting information for: [https://doi.org/10.1021/jm5017686]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1659